The present invention relates generally to the field of motor speed sensing, and more particularly, to an improved arrangement for mounting a speed sensor on a traction motor of a locomotive.
Locomotives typically employ a large diesel engine to drive an alternator, or they are powered by externally supplied electricity. The electric power from the alternator or the external supply is conducted to traction motors located beneath a platform of the locomotive. The traction motors convert the electrical power to rotational mechanical power. The traction motors are engaged to drive wheels through axles. The rotation of the wheels by the traction motors drives the locomotive along its rails.
The electrical power supplied to the traction motors is controlled to regulate the speed of the locomotive. Furthermore, the electrical power supplied to the motors may be regulated to avoid spinning of any one of the drive wheels. In order to properly control the operation of the traction motors, it is necessary to obtain a signal corresponding to the speed of rotation of each respective traction motor.
FIG. 1 illustrates a prior art apparatus utilized to obtain such a motor speed signal. Locomotive traction motor 10 is illustrated from a side view showing the motor frame head 12 which forms part of the motor frame. For locomotives provided by the assignee of the present invention, the motor frame is connected to a truck suspension supporting a truck frame, and the truck is connected to a platform suspension supporting the platform via the locomotive main sills. The frame head 12 is disposed in a generally vertical plane, and it contains a plurality of ventilation openings 14. As is well known in the art, the motor 10 contains a stationary stator portion and a rotating armature portion providing rotation of an output shaft about an axis of rotation 16. A prior art motor speed sensor 18 includes a housing 20 attached to a flange 22. Flange 22 may be formed to be integral with the frame head 12 or is attached thereto, and it extends into the interior of the motor 10 in cantilever form. The flange 22 is disposed on the motor frame head 12 proximate one of the ventilation openings 14. The speed sensor housing 20 is thereby attached to the motor frame head 12 at a distance R1 from the axis of rotation 16. An electrical cable protected within a hose 24 extends from the housing 20 through the ventilation opening 14 and is routed along the exterior of the motor 10. A terminal end of the electrical cable is connected to the locomotive motor control system. One such prior art motor speed sensor 18 is supplied by the General Electric Company, assignee of the present invention, as part number GETS 41A296328BFP1.
The environment of a locomotive traction motor 10 is extremely harsh due to temperature extremes, vibration and shock loadings, dirt and chemical contamination, and magnetic fields. It is desirable to improve the speed sensor design in order to maximize the survivability of this important instrument within its intended environment.
Accordingly, there is described herein an improved traction motor speed sensor support arrangement including: a locomotive traction motor having a frame head adapted for attachment to a locomotive and having an armature portion therein for rotation about an axis of rotation; a sensor housing comprising a base portion attached across the exterior of an opening in the frame head and a sensor portion cantilevered from the base portion and extending through the opening and toward the axis of rotation; and a proximity sensor supported by the sensor portion proximate the armature portion. The mechanical vibration input forces exerted on the speed sensor during the operation of the motor are lowered when compared to prior art devices by mounting the housing to a stiff portion of the motor frame head at a greater distance away from the axis of rotation of the motor.
In another aspect of the invention, the assembly may include a wire connected between the proximity sensor and a connector; the connector comprising a pin portion attached to the wire and a back shell portion attached to the pin portion; and a loop in the wire disposed within the back shell portion of the connector.